Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: quem é a solteira feminina com duplas mistas sendo bernd frohnwieser hilde themel e ano sendo menor que 1959.0
 ###Tabelas: CREATE TABLE diversity_of_new_york_city's_boroughs (diversity_of_new_york_city's_boroughs_id AUTO_INCREMENT PRIMARY KEY, Borough VARCHAR, 1970 INT, 1980 INT, 1990 INT, 2000 INT, 2006 INT) CREATE TABLE new_zealand_tv2 (new_zealand_tv2_id AUTO_INCREMENT PRIMARY KEY, Episode number INT, Title VARCHAR, Original airing VARCHAR, Timeslot VARCHAR, Viewers INT, Top 50 Ranking INT, Scripted Show Ranking INT) CREATE TABLE past_winners (past_winners_id AUTO_INCREMENT PRIMARY KEY, Year INT, Mens singles VARCHAR, Womens singles VARCHAR, Mens doubles VARCHAR, Womens doubles VARCHAR, Mixed doubles VARCHAR) CREATE TABLE list_of_recent_northumberland_cup_winners (list_of_recent_northumberland_cup_winners_id AUTO_INCREMENT PRIMARY KEY, Season VARCHAR, Northumberland Senior Cup VARCHAR, Northumberland Senior Benevolent Bowl VARCHAR, Northumberland Minor Cup VARCHAR, Northumberland Women's Cup VARCHAR) CREATE TABLE german_championship_finals_under_the_gauliga_system (german_championship_finals_under_the_gauliga_system_id AUTO_INCREMENT PRIMARY KEY, Year INT, Champion VARCHAR, Runner-Up VARCHAR, Result VARCHAR, Date VARCHAR, Venue VARCHAR, Attendance VARCHAR)  
SELECT Womens singles FROM past_winners WHERE Mixed doubles = Bernd Frohnwieser Hilde Themel AND Year < 1959.0